It is known to use various superalloy materials, such as cobalt or nickel-based superalloys, for making blades, vanes and other components for power generating turbines, propulsion equipment, etc. These turbines can operate at relatively high temperatures and are generally protected by a series of protective coatings. The coatings may comprise layers of metallic base coats, thermally grown oxide layers, as such layers grow in service-run components and a final ceramic thermal barrier coating (“TBC”). Long-term exposure of these ceramic coatings to the hostile, high temperature, abrasive environment in which such turbines typically operate can cause phase destabilization, sintering, microcracking, delamination and ultimately spallation within the coating layers, exposing the superalloy component and possibly resulting in rapid degradation or failure and potentially requiring costly and burdensome repairs.
U.S. Pat. No. 7,690,840 titled “Method And Apparatus For Measuring On-Line Failure Of Turbine Thermal Barrier Coatings” describes an infrared (IR)-based system configured to non-destructively measure the radiance of a turbine component in a gas turbine in the context of monitoring the formation and progression of TBC defects where images of relative high spatial resolution are needed but where accurate absolute temperature information may not be needed. The foregoing patent is commonly assigned to the assignee of the present invention and is herein incorporated by reference in its entirety.
It would be desirable to acquire two-dimensional IR images of the turbine component to consistently provide accurate absolute temperature measurements of the component. However, temperature measurement errors can be introduced due to various factors, which under prior techniques have not been appropriately accounted for. For example, the emissivity of the TBC can change as a function of wavelength, temperature, age, contamination, etc. Accordingly, it is desirable to provide a system and techniques that overcome the foregoing issues.